SPECT imaging produces two-dimensional tomograms; that is, planar images of the body that are generally oriented either in an axial direction, coronal direction or a sagittal direction. In applying imaging methods, it is well-known to acquire images of multiple slices in the body. This is done either by helical scanning or by individual circular scans while moving the patient step-by-step relative to the scanner.
At the present time, in order to locate a particular ROI in three dimensions in the body, such as one containing a lesion, it is necessary for the radiologist or physician to inspect the many parallel images that have been acquired. For example in a whole body scan it is not unusual to acquire as many as 200 parallel images having one or more of axial, coronal or sagittal orientations. The physician or radiologist in charge of the examination then studies each of the 200 images to determine the location of the lesion in the body. When the location of the lesion is determined, then more detailed scans are undertaken to provide maximum information about the lesion. For example, if the lesion is discovered in an image in the axial plane, then the operator of the equipment will acquire sagittal and coronal, as well as more axial images in the region of interest, to further examine the lesion, for surgical planning, for example. To discover specific lesions, the physician or radiologist in charge of examination must look for “hot” spots that are on the order of one square centimeter, a very time-consuming job.
At the present time, some of the ways used to lessen the burden of reviewing the large group or set of images of slices include cinematic displays of the slice set, and/or a cinematic display of a volume rendered as a 3-D presentation. When using the first of these prior art solutions, the user has to concentrate on the moving presentation in which only one slice is activated at a time. When a lesion is detected, the viewer has to immediately stop the cinematic display and use a cursor to point to the lesion. Then, additional images are taken at the point that the cursor is positioned.
When cinematic volumetric images are displayed, according to the second prior art solution, the display gathers into one view the 3-D information of the slices. Here again, when the lesion is found the viewer has to immediately pause the movie and point to the lesion with the cursor. Then, additional views are taken at the cursor location. These prior art solutions often require additional viewing to locate a lesion.
Maximum intensity projection (MIP) are known in the prior art. It is a commonly used technique in imaging for such things as for displaying 3-D vascular image data. For example, see U.S. Pat. No. 5,570,404 the disclosure of which is hereby included herein by reference. In that patent, the MIP is used for removing undesirable structures from a series of parallel images. As noted in the patent, the MIP frame is developed from a stack of acquired parallel images. The MIP frame contains pixels, wherein each pixel holds the maximum intensity along a ray perpendicular to the MIP frame. The patent does not use the MIP for locational purposes. A preferred aspect of the present invention is to use MIP's for locating regions of interest in a patient being imaged, for example, for locating lesions in the patient. A preferred aspect of the invention also includes displaying the located lesions in three orthogonal planes, or in a 3-D image.